A Wireless Fidelity (English: Wireless Fidelity, WiFi for short) system can operate in a multi-channel/multi-subchannel scenario. For a multi-channel scenario, a channel selection method for maintaining multiple backoff counters on multiple channels is put forward at present. It is assumed that there are N channels in total in the system, and each channel is corresponding to one backoff counter. When a station (STA for short) or an access point (AP for short) needs to send data, the STA or the AP executes the following processes to select a channel for sending the data: randomly generating backoff count values of backoff counters on all the channels, and simultaneously performing carrier sense multiple access (CSMA for short) access on all the channels; when a backoff count value of an idle channel is decreased to 0, preempting the channel; and determining whether the preempted channel meets a bandwidth requirement, and if the preempted channel meets the bandwidth requirement, ending backoff, or if the preempted channel does not meet the bandwidth requirement, determining whether there is an optional idle channel, and if there is an optional idle channel, adjusting a backoff count value of a backoff counter on the idle channel, and continuing to simultaneously perform CSMA access on all idle channels, or if there is no optional idle channel, ending backoff.
However, the inventor finds that a backoff time required by such a channel selection method is long, thereby resulting in low channel utilization.